Learn About the Grape with winemaker Matthew Loso

By: Daniel Hoey

When to Harvest – A Matter of Taste

We were in Walla Walla, Washington right after a harvest that was sped along dramatically by a frost the previous week. I met with Matthew Loso, award-winning Washington state winemaker, and talked with him about harvest – the “crush”.

As we walked through the Ahler Vineyard, where Matt is currently making wine for a new brand, Walla Faces, Matt explained his philosophy regarding one of the most important decisions winemakers make, which is when to harvest grapes. The time of harvest is determined primarily by the ripeness of the grape as measured by sugar, acid and tannin levels with winemakers basing their decision to pick based on the style of wine they wish to produce. As it did last month in Walla Walla, the weather can also speed up the timetable of harvesting. Sugar is measured in the U.S. using the Brix scale, which uses specific gravity to determine the percentage of sugar, by weight. Wine grapes are normally harvested between 19° and 25° Brix.

As grapes ripen, sugar, color and pH increase as total acidity decreases. For the highest quality wine , grapes need to develop aroma and taste characteristics that only result from physiological maturity and sugar-acid balance. Some signs of this maturity are the browning of the grape seeds (pips) and lignation, which is the browning and drying of In recent times there has been more of an emphasis on the "physiological" ripeness of the grape, usually in the form of tannins . While sugar levels and acidity can be measured “in the lab,” currently the only way to measure tannin ripeness is by tasting the grape which can take experience and skill to do accurately.

Matt and I tasted Cabernet grapes in the vineyard – he likes to leave the grapes hang as long as possible, and despite harvest having been completed for most wineries in Walla Walla the Ahler Vineyard still had quite a few grapes on the vine. Matt explained, “Deciding when to pick is all based on taste for me . . . the lab numbers for me are just an estimate of what I’m going to have to do in the winery to get the juice in check.” In other words, its “All About The Grape”!